Until three years ago, both David and Ed thought they were the only branch of the family to have survived the war

In his office overlooking Parliament, David Miliband examines the wedding ring lying in his hand.

It is a gold band, 92 years old, slightly dulled by the passage of time.

It belonged to Samuel Miliband, David and Ed’s grandfather, who bought it when he wed their grandmother Renée in Belgium in 1920.

Renée’s daughter, Nan, gave it to him in 1998, when he married violinist Louise Shackelton.

“To me, this ring represents the chain of history,” Miliband says.

“It has been through war, fascism and post-war reconstruction. It joins me to a terrible, dramatic past.”

It is also a daily reminder of how he and Labour leader Ed, the sons of Jewish refugees, might never have existed.

During the Second World War, 43 of the Miliband family were killed by Nazis.

As a girl: Sofia in Russia

In 1940, as troops began rounding up Jewish men, Samuel brought their 16-year-old father Ralph to England on one of the last boats from Ostend to Dover.

Renée and Nan were trapped for the rest of the war in German-occupied Belgium, where about 25,000 Jews were murdered.

But they were saved by a Catholic farmer and his family in rural Belgium and hidden until 1945.

“They didn’t even know my family well,” Miliband says.

“When I visited them with Aunt Nan in my late teens, I asked the farmer, why did you take in these people whose very presence would lead you to getting shot? He just shrugged and said, ‘One must’.”

Until three years ago, both David and Ed, who spoke movingly of his family’s Jewish roots in his speech at this year’s Labour Party Conference, thought they were the only branch of the family to have survived the war.

But on a visit to Moscow, Ed received a curious message from Echo Radio in Moscow, where he was being interviewed as the UK’s Environment Secretary.

“An 87-year-old lady had phoned and said she was the last surviving Miliband in Russia,” says David.

“She was Sofia, our long-lost cousin several times removed.”

Pre-war: Sofia, right

Sofia Davidovna Miliband is the granddaughter of David and Ed’s great-great-grandfather’s brother.

Her grandfather Osip had a son called David who was Samuel’s cousin. Both were born in the Jewish quarter of Warsaw in Poland.

Samuel moved his family west to Belgium. David moved east to Moscow where he met Pearl and they had daughter Sofia.

A few weeks ago, Miliband, who never knew his grandfather, went to Sofia’s 90th birthday.

He found her an extraordinary woman who survived the war, Stalinism, the break-up the Soviet Union – and came face to face with key political players Churchill and Stalin.

“She is a sparky, lovely woman,” Miliband says. “She is very matter of fact about her life, incredibly modest. I had to coax her life story out of her.”

It left him dumbstruck.

“Sofia was born in 1922, in the stairwell of the building in Moscow she still lives in,” he says.

Survivor: Sofia after the war

“Her father, David, was a salesman from Warsaw. She had this facility for languages, and was the first Miliband to go to university – in 1940.

She was at university at the same time as Stalin’s daughter Svetlana.”

By 1941, Sofia had enlisted in the Soviet Army and was sent to the historic Tehran conference in 1943 where Prime Minister Winston Churchill, US President Franklin D Roosevelt and Soviet leader Joseph Stalin all met for the first time.

“Sofia lived with the chefs at the embassy. Her job was to transcribe the leaders’ conversations,” Miliband says.

Only reported on three days after it had ended, the Tehran conference led to the three countries’ first joint declaration as Allies against the opposing Axis Powers. The Western Allies agreed to open a second front, while the Russians agreed to join the war against Japan.

“I asked her what Churchill was like,” Miliband says. “She didn’t talk to him, but she did see him through a door and he looked ‘kindly with big cheeks’.”

After the war, Sofia returned to university and married Yevgeny, the love of her life, but he died in 1949 of TB.

“He was only 27,” Miliband says. “There is a haunting portrait of him in her flat – his black hair stroked back.

Salesman: Sofia's dad David

"She never married again, never had children. It’s tragic. That’s how she came to be the last Miliband in Russia.

“Sofia is passionate about having found us. She has put up pictures of my kids and Ed’s kids in her flat.

"It no longer feels for her like her family is ending – the Milibands aren’t ending.”

At Sofia’s 90th celebrations, Miliband noticed a birthday card from President Putin.

“It congratulated her on a lifetime of commitment to Russia,” he says.

Getting to know Sofia has been an inspiring journey.

“It is humbling to come face to face with someone who has been through so much,” he says.

He has always tried to explain the difference between his dad’s Marxist views and his own New Labour socialism as rooted their experience of history.

“He was 21 in 1945, and I was 21 in 1986,” he says, simply.

“He had seen war and fascism, the rise of communism, I’d led much more comfortable a life.”

Rowan Griffiths

Ring cycle: With the wedding band

“Sofia’s scars are the living scars of history,” Miliband says. “She is someone who has fought to make the most of life. She survived Stalinism.

“There aren’t many left. They deserve to become part of history, not victims of it.

"Sofia sees herself as just one of millions of Russians who somehow survived.”

David Miliband, the former Foreign Secretary, who fought his brother for the leadership of the Labour Party, has his own place in history too.

Behind him, the sun sets over the Palace of Westminster. And his wedding ring catches the photographer’s flashes.

“Our family’s story shows how history is made up of individual contributions, from one Catholic family in Belgium to a woman in Russia,” Miliband says.